A number of radiological and fluoroscopic imaging systems of various designs are known and are presently in use. Such systems generally are based upon generation of X-rays that are directed toward a subject of interest. The X-rays traverse the subject and impact a digital detector or an image intensifier. In medical contexts, for example, such systems may be used to visualize internal bones, tissues, and organs, and diagnose and treat patient ailments. In other contexts, parts, baggage, parcels, and other subjects may be imaged to assess their contents. In addition, radiological and fluoroscopic imaging systems may be used to identify the structural integrity of objects and for other purposes.
Increasingly, such X-ray systems use digital circuitry, such as solid-state detectors, for detecting the X-rays, which are attenuated, scattered or absorbed by the intervening structures of the subject. It will be appreciated that raw image data acquired via such X-ray systems may include a number of artifacts or other undesirable elements that may, if left uncorrected, result in visual artifacts in a reconstructed image based on the raw image data. In turn, these visual artifacts may negatively impact the ability of a user or computer to discern finer details in the image. For example, non-uniformity of various aspects of the X-ray system, such as the X-ray beam, diodes and/or data channels of a digital detector, and the like, may result in gain variation in the acquired raw image data. While certain approaches for performing gain calibration and correcting image data for such gain variation may be known, these approaches are not applicable to certain types of detectors such as complementary metal-oxide-semiconductor (CMOS) based detectors due to the presence of impulse-type noise generated by direct X-ray hits on the light imager. There is a need, therefore, for improved approaches to gain calibration for digital imaging systems that account for impulse-type noise.